Molding sand



United States Patent T No Drawing. Filed July 30, 1962, Ser. No. 213,094 4 Claims. (Cl. '106-38.35)

This invention relates to molding sands such as are used for the casting of metals, and more particularly to an improvement in molding sands of the type which are bonded with materials other than ordinary clay as such and liquids other than water.

As is well known, in the sand casting of metals a molten metal is poured into a mold formed from a suitable comminuted temperature-resistant mineral, commonly known as sand, and indeed generally consisting of quartz sand, which is bonded by the use of a relatively minor amount of suitable bonding agent, which most commonly has been clay tempered with some water.

In recent years, it has been realized that sand-clay systems of this relatively simple type are not ideally suited to all types of casting, and especially as metal founding technology becomes more and more complex, quite different systems have been developed for sand molds.

An important recent development consists in the utilization of an organophilic clay, using a material such as a petroleum oil to produce the bond. Non-aqueous systems of this type are described, for example, in Canadian Patent 572,142 and U.S. Patent 3,027,265. Even such systems fall short of perfection, however, and the present invention is concerned with improvements in essentially non-aqueous molding sand compositions of this general type.

An object of the present invention is to provide a molding sand containing a completely organic bonding agent which is effective in a non-aqueous lubricant vehicle.

Another object of the invention is to provide a molding sand containing such an organic bonding agent together with an organophilic clay, likewise with the employment of a non-aqueous lubricant.

Other objects of the invention will become apparent as the description thereof proceeds.

Generally speaking, and in accordance With an illustrative embodiment of our invention, we combine, so as to form a molding sand mix: a foundry sand; and a binder which consists of a mixture of a suitable organic liquid as hereinafter described in greater detail, but which may be for example diesel oil, together with a long chain alkyl ammonium humate and which may be conjoined with an organophilic clay in any proportion from zero to four parts of the organophilic clay for each part of the long chain alkyl ammonium humate. While not at all necessary for the practice of the invention, other additives common in the non-aqueous molding sand art may also be present, such as for example silica flour, finely divided iron oxide, and the like. Also, as set forth in detail here inbelow, the organic liquid need not be a single chemical species but may be a mixture of several distinct organic compounds.

Those skilled in the art are well acquainted with foundry sands generally, and consequently these need not be described in any great detail herein save to state that those molding sands commonly used in the conventional claybonded sand molds are likewise well-suited for use in our invention. These are generally quartz sand, the particle size of which may be varied over a wide range, which by way of illustration and not limitation may be, for example, from about 40 to about 175 grain fineness number (GFN) as determined by the standard methods of the American Foundrymens Society. Olivine sand is often 3,210,202 Patented Oct. 5, 1965 used because of its freedom from silicosis hazard; and zircon sand may be used especially for very high temperature casting.

The alkyl ammonium humate is fundamentally an onium salt of humic acid. The humic acid is most readily and economically obtained from lignite, the alkalisoluble portion of which may be considered to be humic acid for the purpose of this invention, and indeed that is the case from a chemical standpoint.

Humic acid is a material of Wide distribution, being present in soils, peat, and coals, especially coals of the type known as lignite or brown coal. Although the exact details of its chemical structure are not completely known, it is a surprisingly uniform substance considering the variety of source materials of which it represents a natural product of degradation, such as leaves, wood, and the like vegetable organic matter. It is an acid, in which both carboxyl and phenolic hydroxyl groups contribute basecombining ability. It is soluble in alkalies, such as caustic soda and sodium carbonate, has a deep brown color, and is readily soluble in water when converted to its alkali metal salt, which may be then termed an alkali metal humate, the commonest example of which is sodium humate.

As indicated, humic acid is present in soils and peat, and may readily be extracted from these by known means, most commonly by treatment with dilute aqueous alkali. Whenever it is a matter of producing a commercial humate, that is, whenever economic considerations are of importance, then the humic acid is nearly always derived from its richest common source, which is lignite, of which there are vast deposits distributed throughout the world, including the United States, and particularly the states of North Dakota, Texas, New Mexico, and California.

The alkyl ammonium humate used in the practice of our invention may be more particularly described as a salt of humic acid, viz., a humate, in which the cation is a substituted ammonium ion, in which one or more of the hydrogen atoms originally present in the ammonium ion is substituted by an alkyl radical, including substituted ammonium cations in which two or more of the substituted positions may form part of a ring (as in the case of imidazolinium), and in which at least one of the said alkyl radicals has from 14 to 22 carbon atoms in a straight chain. It will be clear from this summation that the valence positions of the nitrogen atom which are not occupied by hydrogen atoms may be either long alkyl chains, of the type just described, or may be short alkyl chains, from C to C that is, methyl through tridecyl, or phenyl or benzyl radicals, as long as at least one alkyl radical is present in the range of at least C to C which in the methane series corresponds to tetradecyl through docosyl.

By way of further explanation of the nature and types of the alkyl ammonium humate compounds which we use in our invention, we give the following table showing typical members of the series:

TABLE I Stearylammonium humate Oleylammoniurn humate Palmitylammonium humate Docosylammonium humate Methylstearylammonium humate Laurylstearylammonium humate Butyldocosylammonium humate Diphenylstearylammonium humate Benzyldiethydocosylammonium humate Phenyldibutyloctadecylammonium humate Dimethyldi-(hydrogenated tallow fatty alkyl) ammonium humate Methyltri-(hydrogenated tallow fatty alkyl) ammonium humate l-hydroxyethyl, Z-heptadecenyl, Z-imidazolium humate l-benzyl, l-hydroxyethyl, Z-heptadecyl, Z-imidazolinium humate We use the term alkyl ammonium in the broad sense, wherein ammonium indicates an onium cation in which the basic atom is pentavalent nitrogen. Thus the term includes substituted ammonium cations in which two or more of the substituted positions may form part of a ring, as is the case in the imidazolinium compounds listed above. It will be further understood that the above listing is illustrative and by no means exhaustive.

Generally speaking, the alkyl ammonium humate compounds to be used in our invention may be produced by bringing together humic acid and the alkyl ammonium compound in its base form. The base and the acid neutralize each other with salt formation, so as to produce an alkyl ammonium humate in accordance with the invention. Another general method of preparation is to convert the humic acid to a simple salt by reaction with an alkali, so as to produce sodium humate, potassium humate, ammonium humate, and the like, by reaction with sodium hydroxide, potassium hydroxide, or ammonium hydroxide, respectively. The alkyl ammonium compound is caused to be present in the form of a simple salt. Thus, a primary, secondary, or tertiary amine may be reacted with a simple acid such as hydrochloric, acetic, and the like to give the corresponding substituted ammonium chloride or acetate, respectively. This method of procedure has the advantage that the simple substituted ammonium salts, and the simple humates as described, are both water soluble, so that solutions of each reactant may be made, and the reaction completed by mixing the solutions together. To give a simple example, octadecyl amine is treated with an equivalent quantity of acetic acid to give octadecylammonium acetate. This is then dissolved in several times its weight in water. Separately, humic acid is converted to sodium humate by treating lignite, for example, with sodium hydroxide to neutrality followed by filtering off the insoluble portion of the lignite. The solution of sodium humate thus formed is mixed with the solution of octadecylammonium acetate in stoichiometrically equivalent proportions, whereupon there occurs a quantitative precipitation of octadecylammonium humate. The equivalent weight of the humic acid can readily be determined in any known fashion applicable to acids generally, such as, for example, by titration of sodium hydroxide using an electrometric pH meter.

A somewhat special case is presented by the quaternary substituted ammonium salts, which have no free base form. A simple example is trimethyl octadecylammonium chloride. In its quaternary salt form, it is already available for reaction with an alkali humate such as sodium humate, and it may also be reacted directly with humic acid, although the reaction is accelerated by adding some base such as sodium hydroxide to the reaction mixture to neutralize the acid which is formed as a result of the reaction, which in the particular example considered here would be hydrochloric acid. The quaternary ammonium compounds may be in their hydroxide form, of course, and may then be reacted directly with humic acid.

The organophilic clay is chosen from the group which consists of organophilic montmorillonite and organophilic attapulgite and indeed mixtures thereof in any proportion. Such organophilic clays are now a well known article of commerce, and are described in extensive technical and patent literature. In general, organophilic clays are made by starting with a clay of substantial base exchange capacity, the most commonly used of which are montmorillonite as represented, for example, by Wyoming bentonite or by hectorite, and attapulgite, and etfecting a cation exchange by replacing the bases present in the clay, which may be for example, sodium, calcium, hydrogen and the like, with a long chain onium cation, which indeed is most often a long chain alkyl ammonium ion, and may be chosen from the same class already described hereinabove in connection with the alkyl ammonium humate. Organophilic clays are described in Hauser Patent 2,531,427; Jordan Patent 2,531,440; Miericke Patent 3,027,265; and Canadian Patent 572,142; and indeed many others. They are also described in the book Clay Mineralogy by Ralph E. Grim, New York, 1953, pages 265-269; and in the book entitled The Colloid Chemistry of Silica and Silicates by Ralph K. Iler, Ithaca, 1955, pages 225226. Organophilic clays are commercially available under the trademark Bentone. In general, the organophilic clays commercially available and useful in our invention have within narrow limits the exact amount of long chain onium ion reacted with the clay which corresponds to the cation exchange capacity of the latter. Organophilic clays are generally produced and are commercially available in the form of a fine, dry powder, generally about 200 mesh.

The organic liquid which is used together with the alkyl ammonium humate and, when present, with the organophilic clay in order to form a binder or bonding agent for the sand so as to make it into a moldable composition may be selected from a very large group of organic liquids indeed. We have investigated a large number of organic liquids, and have found that those which are eflfective to form a binder in the fashion described are characterized by having a molecular Weight of at least 125. Suitable organic liquids, which incidentally meet the criterion of molecular weight just stated, are normal octyl alcohol; tall oil; nonyl phenol; various aromatic and paraflinic oils such as diesel oil, fuel oil,

coal tar oil, and the like; the polyethylene glycols commercially available, for example, under the trademark Carbowax and having average molecular weights from about 200 to about 400; the analogous polypropylene glycols which again have molecular weights from about to about 1,000; phosphate esters of ethoxylated alkyl phenols which are commercially available and are described in Chemical and Engineering News, December 25, 1961, page 40; and the like. Mixtures of these various liquids are also quite useful. Examples of the latter are mixtures in various proportions of diesel oil and octyl alcohol; and diesel oil and the phosphate esters just described.

Example 1 Dimethyl-di(hydrogenated tallow) ammonium humate was prepared by mixing together 120.5 parts by weight of North Dakota lignite, of the weathered, alkali-soluble variety described in US. Bur. Mines R.I., 5611, with 22.5 parts water, 16 parts caustic soda, and 44 parts of a commercial dimethyl-di(hydrogenated tallow) ammonium chloride. 200 parts of diesel oil were then added and the entire mixture subjected to high speed agitation for ten minutes. A homogeneous concentrate resulted.

To 5 parts of this concentrate there were added 0.5 part normal octyl alcohol and 94.5 parts of a quartz molding sand of grain fineness number 133. The mixture was mulled in a standard foundry-type muller and then tested; it was designated 1A.

The preparation wasrepeated as above but using 1.0 part normal octyl alcohol and 94.0 parts of the sand. This was designated 1B.

Test results follow:

These very favorable test properties, and the good feel of the mix were substantiated by its use in casting aluminum, which was poured at 1300 F. The performance was excellent, and the collapsibility especially good.

Example 2 Dimethyl-di(hydrogenated tallow) ammonium humate was prepared by mixing together 100 parts by weight of the same lignite as described in Example 1 with 36 parts of a commercial sodium tetraborate decahydrate, and 1000 parts of water. The borax served as an alkalizer to form sodium humate. This mixture was stirred and heated at 170 F. for 45 minutes. 100 parts of a commercial dimethyl-di(hydrogenated tallow) ammonium chloride was then added to the hot mixture and the resulting precipitate was filtered, dried, and ground.

Dimethyl-di(hydrogenated tallow) ammonium montmorillonite was prepared by mixing 90 milliequivalents of a commercial dimethyl-di(hydrogenated tallow) am monium chloride per 100 grams of commercial Wyoming bentonite with enough water to give a consistency appropriate for pugging the mixture, which was about 30 grams of water. A conventional pug mill was used. The resulting extrusions were dried and ground.

1.92 parts by weight of this organophilic montmorillonite were dry blended with 0.96 part of the alkyl ammonium humate so prepared, and this blend was then added to 0.96 part of diesel oil and 96.17 parts of a quartz molding sand of grain fineness number 133. This was then mixed for minutes on a standard laboratory muller. This molding sand composition was tested and had a green compression strength of 6.5 p.s.i.

While we have described our invention with the aid of specific examples and the recitation of various exemplary proportions, reaction conditions, ingredients, and the like, it will be apparent that our invention is a broad one, and that many variations in starting materials, proportions, and the like may be made, all within the scope of the invention as set forth in the claims which follow.

Having described the invention, we claim:

1. A molding sand composition, comprising as essential ingredients sand, and a binder consisting essentially of alkyl ammonium humate, said alkyl having from 14 to 22 carbon atoms in a straight chain, together with from zero to four parts of organophilic clay chosen from the group which consists of organophilic montmorillonite and organophilic attapulgite and mixtures thereof for each part of said alkyl ammonium humate, and an organic liquid having a molecular weight of at least 125 in an amount within the range of 1/10 to 1 /2 part for each part of said alkyl ammonium humate plus said organophilic clay, said molding sand having a green compressive strength of at least 2.4 pounds per square inch.

2. A molding sand composition, comprising as essential ingredients sand, and from about 1 to about 10 parts per parts of said sand of a binder consisting essentially of alkyl ammonium humate, said alkyl having from 14 to 22 carbon atoms in a straight chain, together with from zero to four parts of organophilic clay chosen from the group which consists of organophilic montmorillonite and organophilic attapulgite and mixtures thereof for each part of said alkyl ammonium humate, and an organic liquid having a molecular weight of at least in an amount within the range of 1/ 10 to 1 /2 part for each part of said alkyl ammonium humate plus said organophilic clay, said molding sand having a green compressive strength of at least 2.4 pounds per square inch.

3. A molding sand composition, comprising as essential constituents sand, and a binder consisting essentially of alkyl ammonium humate, said alkyl having from 14 to 22 carbon atoms in a straight chain, together with from zero to four parts of organophilic montmorillonite and organophilic attapulgite and mixtures thereof for each part of said alkyl ammonium humate, and an organic liquid having a molecular weight of at least 125 in an amount suflicient to impart to said molding sand a green compressive strength of at least 2.4 pounds per square inch.

4. A molding sand composition, comprising as essential constituents sand, and a binder consisting essentially of alkyl ammonium humate, said alkyl having from 14 to 22 carbon atoms in a straight chain, together with from Zero to four parts of organophilic montmorillonite and organophilic attapnlgite and mixtures thereof for each part of said alkyl ammonium humate, and an organic liquid of a kind and in an amount sufllcient to impart to said molding sand a green compressive strength of at least 2.4 pounds per square inch.

No references cited.

ALEXANDER H. BRODMERKEL, Primary Examiner. MORRIS LIEBMAN, Examiner. 

1. A MOLDING SAND COMPOSITION, COMPRISING AS ESSENTIAL INGREDIENTS SAND, AND A BINDER CONSISTING ESSENTIALLY OF ALKYL AMMONIUM HUMATE, SAID ALKYL HAVING FROM 14 TO 22 CARBON ATOMS IN A STRAIGHT CHAIN, TOGETHER WITH FROM ZERO TO FOUR PARTS OF ORGANOPHILIC CLAY CHOSEN FROM THE GROUP WHICH CONSISTS OF ORGANOPHILIC MONTMORILLONITE AND ORGANOPHILIC ATTAPULGITE AND MIXTURES THEREOF FOR EACH PART OF SAID ALKYL AMMONIUM HUMATE, AND AN ORGANIC LIQUID HAVING A MOLECULAR WEIGHT OF AT LEAST 125 IN AN AMOUNT WITHIN THE RANGE OF 1/10 TO 1 1/2 PART FOR EACH PART OF SAID ALKYL AMMONIUM HUMATE PLUS SAID ORGANOPHILIC CLAY, SAID MOLDING SAND HAVING A GREEN COMPRESSIVE STRENGTH OF AT LEAST 2.4 POUNDS PER SQUARE INCH. 